FIG. 1.

(A) Structure of the LPS core oligosaccharide from S. enterica serovar Typhimurium (20). The inner core heptose region is highlighted by shading. Genetic determinants for the modification of the inner core heptose region (conserved between E. coli and S. enterica) are shown, and they must function in the following sequence: waaP, waaQ, and then waaY (43). Abbreviations: Hep, l-glycero-d-manno-heptose; Kdo, 3-deoxy-d-manno-oct-2-ulosonic acid; P, phosphate; PS, polysaccharide. ∗, the PEtN substitution is nonstoichiometric but is reportedly present in larger amounts in PM-resistant mutants of S. enterica (16). (B) Predicted structure of the LPS core oligosaccharide from CWG304, based on the function of WaaP in E. coli F470 and its effect on WaaQ and WaaY activities (43).